/*
 Copyright (c) 1997, 1998 Carnegie Mellon University.  All Rights
 Reserved.

 Redistribution and use in source and binary forms, with or without
 modification, are permitted provided that the following conditions are met:

 1. Redistributions of source code must retain the above copyright notice,
 this list of conditions and the following disclaimer.
 2. Redistributions in binary form must reproduce the above copyright notice,
 this list of conditions and the following disclaimer in the documentation
 and/or other materials provided with the distribution.
 3. The name of the author may not be used to endorse or promote products
 derived from this software without specific prior written permission.

 THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
 OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
 WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
 OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
 ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

 The MAODV code developed by the CMU/MONARCH group was optimized and tuned by
 Samir Das and Mahesh Marina, University of Cincinnati. The work was partially
 done in Sun Microsystems.

 Modified for gratuitous replies by Anant Utgikar, 09/16/02.
 */

#include <random.h>
#include <cmu-trace.h>

#include "nsmiracle_aodv.h"
#include "nsmiracle_aodv_packet.h"


#define max(a,b)        ( (a) > (b) ? (a) : (b) )
#define CURRENT_TIME    Scheduler::instance().clock()

//#define DEBUG
//#define ERROR

#ifdef DEBUG
static int extra_route_reply = 0;
static int limit_route_request = 0;
static int route_request = 0;
#endif

/*
 TCL Hooks
 */

int hdr_maodv::offset_;
static class MAODVHeaderClass: public PacketHeaderClass {
public:
    MAODVHeaderClass() :
        PacketHeaderClass("PacketHeader/MAODV", sizeof(hdr_all_maodv)) {
        bind_offset(&hdr_maodv::offset_);
        bind();
    }
} class_MAODVHeader;

static class MAODVclass: public TclClass {
public:
    MAODVclass() :
        TclClass("Agent/MAODV") {
    }
    TclObject* create(int argc, const char* const * argv) {
        assert(argc == 5);

        return (new MAODV((nsaddr_t) Address::instance().str2addr(argv[4])));
    }
} class_rtProtoMAODV;

int MAODV::command(int argc, const char* const * argv) {
    if (argc == 2) {
        Tcl& tcl = Tcl::instance();

        if (strncasecmp(argv[1], "id", 2) == 0) {
            tcl.resultf("%d", index);
            return TCL_OK;
        }

        if (strncasecmp(argv[1], "start", 2) == 0) {
            btimer.handle((Event*) 0);

#ifndef MAODV_LINK_LAYER_DETECTION
            htimer.handle((Event*) 0);
            ntimer.handle((Event*) 0);
#endif // LINK LAYER DETECTION
            rtimer.handle((Event*) 0);
            return TCL_OK;
        }
    } else if (argc == 3) {
        if (strcmp(argv[1], "index") == 0) {
            index = atoi(argv[2]);
            return TCL_OK;
        }

        else if (strcmp(argv[1], "log-target") == 0 || strcmp(argv[1],
                "tracetarget") == 0) {
            logtarget = (Trace*) TclObject::lookup(argv[2]);
            if (logtarget == 0)
                return TCL_ERROR;
            return TCL_OK;
        } else if (strcmp(argv[1], "drop-target") == 0) {
            int stat = rqueue.command(argc, argv);
            if (stat != TCL_OK)
                return stat;
            return Agent::command(argc, argv);
        } else if (strcmp(argv[1], "if-queue") == 0) {
            ifqueue = (PriQueue*) TclObject::lookup(argv[2]);

            if (ifqueue == 0)
                return TCL_ERROR;
            return TCL_OK;
        } else if (strcmp(argv[1], "port-dmux") == 0) {
            dmux_ = (PortClassifier *) TclObject::lookup(argv[2]);
            if (dmux_ == 0) {
                fprintf(stderr, "%s: %s lookup of %s failed\n", __FILE__,
                        argv[1], argv[2]);
                return TCL_ERROR;
            }
            return TCL_OK;
        }
    }
    return Agent::command(argc, argv);
}

/*
 Constructor
 */
MAODV::MAODV(nsaddr_t id) :
    Agent(PT_MAODV), btimer(this), htimer(this), ntimer(this), rtimer(this),
            lrtimer(this), rqueue() {

    index = id;
    seqno = 2;
    bid = 1;

    LIST_INIT(&nbhead);
    LIST_INIT(&bihead);

    logtarget = 0;
    ifqueue = 0;
}

/*
 Timers
 */
void MAODVBroadcastTimer::handle(Event*) {
    agent->id_purge();
    Scheduler::instance().schedule(this, &intr, MADOV_BCAST_ID_SAVE);
}

void MAODVHelloTimer::handle(Event*) {
    agent->sendHello();
    double interval = MADOV_MIN_HELLO_INTERVAL + ((MADOV_MAX_HELLO_INTERVAL - MADOV_MIN_HELLO_INTERVAL)
            * Random::uniform());
    assert(interval >= 0);
    Scheduler::instance().schedule(this, &intr, interval);
}

void MAODVNeighborTimer::handle(Event*) {
    agent->nb_purge();
    Scheduler::instance().schedule(this, &intr, MADOV_HELLO_INTERVAL);
}

void MAODVRouteCacheTimer::handle(Event*) {
    agent->rt_purge();
#define FREQUENCY 0.5 // sec
    Scheduler::instance().schedule(this, &intr, FREQUENCY);
}

void MAODVLocalRepairTimer::handle(Event* p) { // SRD: 5/4/99
    maodv_rt_entry *rt;
    struct hdr_ip *ih = HDR_IP((Packet *) p);

    /* you get here after the timeout in a local repair attempt */
    /*	fprintf(stderr, "%s\n", __FUNCTION__); */

    rt = agent->rtable.rt_lookup(ih->daddr());

    if (rt && rt->rt_flags != RTF_UP) {
        // route is yet to be repaired
        // I will be conservative and bring down the route
        // and send route errors upstream.
        /* The following assert fails, not sure why */
        /* assert (rt->rt_flags == RTF_IN_REPAIR); */

        //rt->rt_seqno++;
        agent->rt_down(rt);
        // send RERR
#ifdef DEBUG
        fprintf(stderr,"Node %d: Dst - %d, failed local repair\n",index, rt->rt_dst);
#endif
    }
    Packet::free((Packet *) p);
}

/*
 Broadcast ID Management  Functions
 */
void MAODV::id_insert(nsaddr_t id, u_int32_t bid) {
    MAODVBroadcastID *b = new MAODVBroadcastID(id, bid);

    assert(b);
    b->expire = CURRENT_TIME + MADOV_BCAST_ID_SAVE;
    LIST_INSERT_HEAD(&bihead, b, link);
}

/* SRD */
bool MAODV::id_lookup(nsaddr_t id, u_int32_t bid) {
    MAODVBroadcastID *b = bihead.lh_first;

    // Search the list for a match of source and bid
    for (; b; b = b->link.le_next) {
        if ((b->src == id) && (b->id == bid))
            return true;
    }
    return false;
}

void MAODV::id_purge() {
    MAODVBroadcastID *b = bihead.lh_first;
    MAODVBroadcastID *bn;
    double now = CURRENT_TIME;

    for (; b; b = bn) {
        bn = b->link.le_next;
        if (b->expire <= now) {
            LIST_REMOVE(b, link);
            delete b;
        }
    }
}

/*
 Helper Functions
 */
double MAODV::PerHopTime(maodv_rt_entry *rt) {
    int num_non_zero = 0, i;
    double total_latency = 0.0;

    if (!rt)
        return ((double) MADOV_NODE_TRAVERSAL_TIME);

    for (i = 0; i < MAX_HISTORY; i++) {
        if (rt->rt_disc_latency[i] > 0.0) {
            num_non_zero++;
            total_latency += rt->rt_disc_latency[i];
        }
    }
    if (num_non_zero > 0)
        return (total_latency / (double) num_non_zero);
    else
        return ((double) MADOV_NODE_TRAVERSAL_TIME);

}

/*
 Link Failure Management Functions
 */
static void maodv_rt_failed_callback(Packet *p, void *arg) {
    ((MAODV*) arg)->rt_ll_failed(p);
}

/*
 * This routine is invoked when the link-layer reports a route failed.
 */
void MAODV::rt_ll_failed(Packet *p) {
    struct hdr_cmn *ch = HDR_CMN(p);
    struct hdr_ip *ih = HDR_IP(p);
    maodv_rt_entry *rt;
    nsaddr_t broken_nbr = ch->next_hop_;

#ifndef MAODV_LINK_LAYER_DETECTION
    drop(p, DROP_RTR_MAC_CALLBACK);
#else

    /*
     * Non-data packets and Broadcast Packets can be dropped.
     */
    if(! DATA_PACKET(ch->ptype()) ||
            (u_int32_t) ih->daddr() == IP_BROADCAST) {
        drop(p, DROP_RTR_MAC_CALLBACK);
        return;
    }
    log_link_broke(p);
    if((rt = rtable.rt_lookup(ih->daddr())) == 0) {
        drop(p, DROP_RTR_MAC_CALLBACK);
        return;
    }
    log_link_del(ch->next_hop_);

#ifdef MAODV_LOCAL_REPAIR
    /* if the broken link is closer to the dest than source,
     attempt a local repair. Otherwise, bring down the route. */

    if (ch->num_forwards() > rt->rt_hops) {
        local_rt_repair(rt, p); // local repair
        // retrieve all the packets in the ifq using this link,
        // queue the packets for which local repair is done,
        return;
    }
    else
#endif // LOCAL REPAIR
    {
        drop(p, DROP_RTR_MAC_CALLBACK);
        // Do the same thing for other packets in the interface queue using the
        // broken link -Mahesh
        while((p = ifqueue->filter(broken_nbr))) {
            drop(p, DROP_RTR_MAC_CALLBACK);
        }
        nb_delete(broken_nbr);
    }

#endif // LINK LAYER DETECTION
}

void MAODV::handle_link_failure(nsaddr_t id) {
    maodv_rt_entry *rt, *rtn;
    Packet *rerr = Packet::alloc();
    struct hdr_maodv_error *re = HDR_MAODV_ERROR(rerr);

    re->DestCount = 0;
    for (rt = rtable.head(); rt; rt = rtn) { // for each rt entry
        rtn = rt->rt_link.le_next;
        if ((rt->rt_hops != INFINITY2) && (rt->rt_nexthop == id)) {
            assert(rt->rt_flags == RTF_UP);
            assert((rt->rt_seqno % 2) == 0);
            rt->rt_seqno++;
            re->unreachable_dst[re->DestCount] = rt->rt_dst;
            re->unreachable_dst_seqno[re->DestCount] = rt->rt_seqno;
#ifdef DEBUG
            fprintf(stderr, "%s(%f): %d\t(%d\t%u\t%d)\n", __FUNCTION__, CURRENT_TIME,
                    index, re->unreachable_dst[re->DestCount],
                    re->unreachable_dst_seqno[re->DestCount], rt->rt_nexthop);
#endif // DEBUG
            re->DestCount += 1;
            rt_down(rt);
        }
        // remove the lost neighbor from all the precursor lists
        rt->pc_delete(id);
    }

    if (re->DestCount > 0) {
#ifdef DEBUG
        fprintf(stderr, "%s(%f): %d\tsending RERR...\n", __FUNCTION__, CURRENT_TIME, index);
#endif // DEBUG
        sendError(rerr, false);
    } else {
        Packet::free(rerr);
    }
}

void MAODV::local_rt_repair(maodv_rt_entry *rt, Packet *p) {
#ifdef DEBUG
    fprintf(stderr,"%s: Dst - %d\n", __FUNCTION__, rt->rt_dst);
#endif
    // Buffer the packet
    rqueue.enque(p);

    // mark the route as under repair
    rt->rt_flags = RTF_IN_REPAIR;

    sendRequest(rt->rt_dst);

    // set up a timer interrupt
    Scheduler::instance().schedule(&lrtimer, p->copy(), rt->rt_req_timeout);
}

void MAODV::rt_update(maodv_rt_entry *rt, u_int32_t seqnum, u_int16_t metric,
        nsaddr_t nexthop, double expire_time) {

    rt->rt_seqno = seqnum;
    rt->rt_hops = metric;
    rt->rt_flags = RTF_UP;
    rt->rt_nexthop = nexthop;
    rt->rt_expire = expire_time;
}

void MAODV::rt_down(maodv_rt_entry *rt) {
    /*
     *  Make sure that you don't "down" a route more than once.
     */

    if (rt->rt_flags == RTF_DOWN) {
        return;
    }

    // assert (rt->rt_seqno%2); // is the seqno odd?
    rt->rt_last_hop_count = rt->rt_hops;
    rt->rt_hops = INFINITY2;
    rt->rt_flags = RTF_DOWN;
    rt->rt_nexthop = 0;
    rt->rt_expire = 0;

} /* rt_down function */

/*
 Route Handling Functions
 */

void MAODV::rt_resolve(Packet *p) {
    struct hdr_cmn *ch = HDR_CMN(p);
    struct hdr_ip *ih = HDR_IP(p);
    maodv_rt_entry *rt;

    /*
     *  Set the transmit failure callback.  That
     *  won't change.
     */
    ch->xmit_failure_ = maodv_rt_failed_callback;
    ch->xmit_failure_data_ = (void*) this;
    rt = rtable.rt_lookup(ih->daddr());
    if (rt == 0) {
        rt = rtable.rt_add(ih->daddr());
    }

    /*
     * If the route is up, forward the packet
     */

    if (rt->rt_flags == RTF_UP) {
        assert(rt->rt_hops != INFINITY2);
        forward(rt, p, MADOV_NO_DELAY);
    }
    /*
     *  if I am the source of the packet, then do a Route Request.
     */
    else if (ih->saddr() == index) {
        rqueue.enque(p);
        sendRequest(rt->rt_dst);
    }
    /*
     *	A local repair is in progress. Buffer the packet.
     */
    else if (rt->rt_flags == RTF_IN_REPAIR) {
        rqueue.enque(p);
    }

    /*
     * I am trying to forward a packet for someone else to which
     * I don't have a route.
     */
    else {
        Packet *rerr = Packet::alloc();
        struct hdr_maodv_error *re = HDR_MAODV_ERROR(rerr);
        /*
         * For now, drop the packet and send error upstream.
         * Now the route errors are broadcast to upstream
         * neighbors - Mahesh 09/11/99
         */

        assert(rt->rt_flags == RTF_DOWN);
        re->DestCount = 0;
        re->unreachable_dst[re->DestCount] = rt->rt_dst;
        re->unreachable_dst_seqno[re->DestCount] = rt->rt_seqno;
        re->DestCount += 1;
#ifdef DEBUG
        fprintf(stderr, "%s: sending RERR...\n", __FUNCTION__);
#endif
        sendError(rerr, false);

        drop(p, DROP_RTR_NO_ROUTE);
    }

}

void MAODV::rt_purge() {
    maodv_rt_entry *rt, *rtn;
    double now = CURRENT_TIME;
    double delay = 0.0;
    Packet *p;

    for (rt = rtable.head(); rt; rt = rtn) { // for each rt entry
        rtn = rt->rt_link.le_next;
        if ((rt->rt_flags == RTF_UP) && (rt->rt_expire < now)) {
            // if a valid route has expired, purge all packets from
            // send buffer and invalidate the route.
            assert(rt->rt_hops != INFINITY2);
            while ((p = rqueue.deque(rt->rt_dst))) {
#ifdef DEBUG
                fprintf(stderr, "%s: calling drop()\n",
                        __FUNCTION__);
#endif // DEBUG
                drop(p, DROP_RTR_NO_ROUTE);
            }
            rt->rt_seqno++;
            assert(rt->rt_seqno % 2);
            rt_down(rt);
        } else if (rt->rt_flags == RTF_UP) {
            // If the route is not expired,
            // and there are packets in the sendbuffer waiting,
            // forward them. This should not be needed, but this extra
            // check does no harm.
            assert(rt->rt_hops != INFINITY2);
            while ((p = rqueue.deque(rt->rt_dst))) {
                forward(rt, p, delay);
                delay += MADOV_ARP_DELAY;
            }
        } else if (rqueue.find(rt->rt_dst))
            // If the route is down and
            // if there is a packet for this destination waiting in
            // the sendbuffer, then send out route request. sendRequest
            // will check whether it is time to really send out request
            // or not.
            // This may not be crucial to do it here, as each generated
            // packet will do a sendRequest anyway.

            sendRequest(rt->rt_dst);
    }

}

/*
 Packet Reception Routines
 */

void MAODV::recv(Packet *p, Handler*) {
    struct hdr_cmn *ch = HDR_CMN(p);
    struct hdr_ip *ih = HDR_IP(p);

    assert( initialized());
    //assert(p->incoming == 0);
    // XXXXX NOTE: use of incoming flag has been depracated; In order to track direction of pkt flow, direction_ in hdr_cmn is used instead. see packet.h for details.

    if (ch->ptype() == PT_MAODV) {
        ih->ttl_ -= 1;
        recvMAODV(p);
        return;
    }

    /*
     *  Must be a packet I'm originating...
     */
    if ((ih->saddr() == index) && (ch->num_forwards() == 0)) {
        /*
         * Add the IP Header.
         * TCP adds the IP header too, so to avoid setting it twice, we check if
         * this packet is not a TCP or ACK segment.
         */
        if (ch->ptype() != PT_TCP && ch->ptype() != PT_ACK) {
            ch->size() += IP_HDR_LEN;
        }
        // Added by Parag Dadhania && John Novatnack to handle broadcasting
        if ((u_int32_t) ih->daddr() != IP_BROADCAST) {
            ih->ttl_ = MADOV_NETWORK_DIAMETER;
        }
    }
    /*
     *  I received a packet that I sent.  Probably
     *  a routing loop.
     */
    else if (ih->saddr() == index) {
        drop(p, DROP_RTR_ROUTE_LOOP);
        return;
    }
    /*
     *  Packet I'm forwarding...
     */
    else {
        /*
         *  Check the TTL.  If it is zero, then discard.
         */
        if (--ih->ttl_ == 0) {
            drop(p, DROP_RTR_TTL);
            return;
        }
    }
    // Added by Parag Dadhania && John Novatnack to handle broadcasting
    if ((u_int32_t) ih->daddr() != IP_BROADCAST)
        rt_resolve(p);
    else
        forward((maodv_rt_entry*) 0, p, MADOV_NO_DELAY);
}

void MAODV::recvMAODV(Packet *p) {
    struct hdr_maodv *ah = HDR_MAODV(p);

    assert(HDR_IP(p)->sport() == RT_PORT);
    assert(HDR_IP(p)->dport() == RT_PORT);

    /*
     * Incoming Packets.
     */
    switch (ah->ah_type) {

    case MAODVTYPE_RREQ:
        recvRequest(p);
        break;

    case MAODVTYPE_RREP:
        recvReply(p);
        break;

    case MAODVTYPE_RERR:
        recvError(p);
        break;

    case MAODVTYPE_HELLO:
        recvHello(p);
        break;

    default:
        fprintf(stderr, "Invalid MAODV type (%x)\n", ah->ah_type);
        exit(1);
    }

}

void MAODV::recvRequest(Packet *p) {
    struct hdr_ip *ih = HDR_IP(p);
    struct hdr_maodv_request *rq = HDR_MAODV_REQUEST(p);
    maodv_rt_entry *rt;

    /*
     * Drop if:
     *      - I'm the source
     *      - I recently heard this request.
     */

    if (rq->rq_src == index) {
#ifdef DEBUG
        fprintf(stderr, "%s: got my own REQUEST\n", __FUNCTION__);
#endif // DEBUG
        Packet::free(p);
        return;
    }

    if (id_lookup(rq->rq_src, rq->rq_bcast_id)) {

#ifdef DEBUG
        fprintf(stderr, "%s: discarding request\n", __FUNCTION__);
#endif // DEBUG
        Packet::free(p);
        return;
    }

    /*
     * Cache the broadcast ID
     */
    id_insert(rq->rq_src, rq->rq_bcast_id);

    /*
     * We are either going to forward the REQUEST or generate a
     * REPLY. Before we do anything, we make sure that the REVERSE
     * route is in the route table.
     */
    maodv_rt_entry *rt0; // rt0 is the reverse route

    rt0 = rtable.rt_lookup(rq->rq_src);
    if (rt0 == 0) { /* if not in the route table */
        // create an entry for the reverse route.
        rt0 = rtable.rt_add(rq->rq_src);
    }

    rt0->rt_expire = max(rt0->rt_expire, (CURRENT_TIME + MADOV_REV_ROUTE_LIFE));

    if ((rq->rq_src_seqno > rt0->rt_seqno) || ((rq->rq_src_seqno
            == rt0->rt_seqno) && (rq->rq_hop_count < rt0->rt_hops))) {
        // If we have a fresher seq no. or lesser #hops for the
        // same seq no., update the rt entry. Else don't bother.
        rt_update(rt0, rq->rq_src_seqno, rq->rq_hop_count, ih->saddr(),
                max(rt0->rt_expire, (CURRENT_TIME + MADOV_REV_ROUTE_LIFE)));
        if (rt0->rt_req_timeout > 0.0) {
            // Reset the soft state and
            // Set expiry time to CURRENT_TIME + MADOV_ACTIVE_ROUTE_TIMEOUT
            // This is because route is used in the forward direction,
            // but only sources get benefited by this change
            rt0->rt_req_cnt = 0;
            rt0->rt_req_timeout = 0.0;
            rt0->rt_req_last_ttl = rq->rq_hop_count;
            rt0->rt_expire = CURRENT_TIME + MADOV_ACTIVE_ROUTE_TIMEOUT;
        }

        /* Find out whether any buffered packet can benefit from the
         * reverse route.
         * May need some change in the following code - Mahesh 09/11/99
         */
        assert(rt0->rt_flags == RTF_UP);
        Packet *buffered_pkt;
        while ((buffered_pkt = rqueue.deque(rt0->rt_dst))) {
            if (rt0 && (rt0->rt_flags == RTF_UP)) {
                assert(rt0->rt_hops != INFINITY2);
                forward(rt0, buffered_pkt, MADOV_NO_DELAY);
            }
        }
    }
    // End for putting reverse route in rt table


    /*
     * We have taken care of the reverse route stuff.
     * Now see whether we can send a route reply.
     */

    rt = rtable.rt_lookup(rq->rq_dst);

    // First check if I am the destination ..

    if (rq->rq_dst == index) {

#ifdef DEBUG
        fprintf(stderr, "%d - %s: destination sending reply\n",
                index, __FUNCTION__);
#endif // DEBUG

        // Just to be safe, I use the max. Somebody may have
        // incremented the dst seqno.
        seqno = max(seqno, rq->rq_dst_seqno) + 1;
        if (seqno % 2)
            seqno++;

        sendReply(rq->rq_src, // IP Destination
                1, // Hop Count
                index, // Dest IP Address
                seqno, // Dest Sequence Num
                MADOV_ROUTE_TIMEOUT, // Lifetime
                rq->rq_timestamp); // timestamp

        Packet::free(p);
    }

    // I am not the destination, but I may have a fresh enough route.

    else if (rt && (rt->rt_hops != INFINITY2) && (rt->rt_seqno
            >= rq->rq_dst_seqno)) {

        //assert (rt->rt_flags == RTF_UP);
        assert(rq->rq_dst == rt->rt_dst);
        //assert ((rt->rt_seqno%2) == 0);	// is the seqno even?
        sendReply(rq->rq_src, rt->rt_hops + 1, rq->rq_dst, rt->rt_seqno,
                (u_int32_t)(rt->rt_expire - CURRENT_TIME),
                //             rt->rt_expire - CURRENT_TIME,
                rq->rq_timestamp);
        // Insert nexthops to RREQ source and RREQ destination in the
        // precursor lists of destination and source respectively
        rt->pc_insert(rt0->rt_nexthop); // nexthop to RREQ source
        rt0->pc_insert(rt->rt_nexthop); // nexthop to RREQ destination

#ifdef RREQ_GRAT_RREP

        sendReply(rq->rq_dst,
                rq->rq_hop_count,
                rq->rq_src,
                rq->rq_src_seqno,
                (u_int32_t) (rt->rt_expire - CURRENT_TIME),
                //             rt->rt_expire - CURRENT_TIME,
                rq->rq_timestamp);
#endif

        // TODO: send grat RREP to dst if G flag set in RREQ using rq->rq_src_seqno, rq->rq_hop_counT

        // DONE: Included gratuitous replies to be sent as per IETF maodv draft specification. As of now, G flag has not been dynamically used and is always set or reset in maodv-packet.h --- Anant Utgikar, 09/16/02.

        Packet::free(p);
    }
    /*
     * Can't reply. So forward the  Route Request
     */
    else {
        ih->saddr() = index;
        ih->daddr() = IP_BROADCAST;
        rq->rq_hop_count += 1;
        // Maximum sequence number seen en route
        if (rt)
            rq->rq_dst_seqno = max(rt->rt_seqno, rq->rq_dst_seqno);
        forward((maodv_rt_entry*) 0, p, MADOV_DELAY);
    }

}

void MAODV::recvReply(Packet *p) {
    //struct hdr_cmn *ch = HDR_CMN(p);
    struct hdr_ip *ih = HDR_IP(p);
    struct hdr_maodv_reply *rp = HDR_MAODV_REPLY(p);
    maodv_rt_entry *rt;
    char suppress_reply = 0;
    double delay = 0.0;

#ifdef DEBUG
    fprintf(stderr, "%d - %s: received a REPLY\n", index, __FUNCTION__);
#endif // DEBUG

    /*
     *  Got a reply. So reset the "soft state" maintained for
     *  route requests in the request table. We don't really have
     *  have a separate request table. It is just a part of the
     *  routing table itself.
     */
    // Note that rp_dst is the dest of the data packets, not the
    // the dest of the reply, which is the src of the data packets.

    rt = rtable.rt_lookup(rp->rp_dst);

    /*
     *  If I don't have a rt entry to this host... adding
     */
    if (rt == 0) {
        rt = rtable.rt_add(rp->rp_dst);
    }

    /*
     * Add a forward route table entry... here I am following
     * Perkins-Royer MAODV paper almost literally - SRD 5/99
     */

    if ((rt->rt_seqno < rp->rp_dst_seqno) || // newer route
            ((rt->rt_seqno == rp->rp_dst_seqno) && (rt->rt_hops
                    > rp->rp_hop_count))) { // shorter or better route

        // Update the rt entry
        rt_update(rt, rp->rp_dst_seqno, rp->rp_hop_count, rp->rp_src,
                CURRENT_TIME + rp->rp_lifetime);

        // reset the soft state
        rt->rt_req_cnt = 0;
        rt->rt_req_timeout = 0.0;
        rt->rt_req_last_ttl = rp->rp_hop_count;

        if (ih->daddr() == index) { // If I am the original source
            // Update the route discovery latency statistics
            // rp->rp_timestamp is the time of request origination

            rt->rt_disc_latency[(unsigned char) rt->hist_indx] = (CURRENT_TIME
                    - rp->rp_timestamp) / (double) rp->rp_hop_count;
            // increment indx for next time
            rt->hist_indx = (rt->hist_indx + 1) % MAX_HISTORY;
        }

        /*
         * Send all packets queued in the sendbuffer destined for
         * this destination.
         * XXX - observe the "second" use of p.
         */
        Packet *buf_pkt;
        while ((buf_pkt = rqueue.deque(rt->rt_dst))) {
            if (rt->rt_hops != INFINITY2) {
                assert(rt->rt_flags == RTF_UP);
                // Delay them a little to help ARP. Otherwise ARP
                // may drop packets. -SRD 5/23/99
                forward(rt, buf_pkt, delay);
                delay += MADOV_ARP_DELAY;
            }
        }
    } else {
        suppress_reply = 1;
    }

    /*
     * If reply is for me, discard it.
     */

    if (ih->daddr() == index || suppress_reply) {
        Packet::free(p);
    }
    /*
     * Otherwise, forward the Route Reply.
     */
    else {
        // Find the rt entry
        maodv_rt_entry *rt0 = rtable.rt_lookup(ih->daddr());
        // If the rt is up, forward
        if (rt0 && (rt0->rt_hops != INFINITY2)) {
            assert(rt0->rt_flags == RTF_UP);
            rp->rp_hop_count += 1;
            rp->rp_src = index;
            forward(rt0, p, MADOV_NO_DELAY);
            // Insert the nexthop towards the RREQ source to
            // the precursor list of the RREQ destination
            rt->pc_insert(rt0->rt_nexthop); // nexthop to RREQ source

        } else {
            // I don't know how to forward .. drop the reply.
#ifdef DEBUG
            fprintf(stderr, "%s: dropping Route Reply\n", __FUNCTION__);
#endif // DEBUG
            drop(p, DROP_RTR_NO_ROUTE);
        }
    }
}

void MAODV::recvError(Packet *p) {
    struct hdr_ip *ih = HDR_IP(p);
    struct hdr_maodv_error *re = HDR_MAODV_ERROR(p);
    maodv_rt_entry *rt;
    u_int8_t i;
    Packet *rerr = Packet::alloc();
    struct hdr_maodv_error *nre = HDR_MAODV_ERROR(rerr);

    nre->DestCount = 0;

    for (i = 0; i < re->DestCount; i++) {
        // For each unreachable destination
        rt = rtable.rt_lookup(re->unreachable_dst[i]);
        if (rt && (rt->rt_hops != INFINITY2) && (rt->rt_nexthop == ih->saddr())
                && (rt->rt_seqno <= re->unreachable_dst_seqno[i])) {
            assert(rt->rt_flags == RTF_UP);
            assert((rt->rt_seqno % 2) == 0); // is the seqno even?
#ifdef DEBUG
            fprintf(stderr, "%s(%f): %d\t(%d\t%u\t%d)\t(%d\t%u\t%d)\n", __FUNCTION__,CURRENT_TIME,
                    index, rt->rt_dst, rt->rt_seqno, rt->rt_nexthop,
                    re->unreachable_dst[i],re->unreachable_dst_seqno[i],
                    ih->saddr());
#endif // DEBUG
            rt->rt_seqno = re->unreachable_dst_seqno[i];
            rt_down(rt);

            // Not sure whether this is the right thing to do
            Packet *pkt;
            while ((pkt = ifqueue->filter(ih->saddr()))) {
                drop(pkt, DROP_RTR_MAC_CALLBACK);
            }

            // if precursor list non-empty add to RERR and delete the precursor list
            if (!rt->pc_empty()) {
                nre->unreachable_dst[nre->DestCount] = rt->rt_dst;
                nre->unreachable_dst_seqno[nre->DestCount] = rt->rt_seqno;
                nre->DestCount += 1;
                rt->pc_delete();
            }
        }
    }

    if (nre->DestCount > 0) {
#ifdef DEBUG
        fprintf(stderr, "%s(%f): %d\t sending RERR...\n", __FUNCTION__, CURRENT_TIME, index);
#endif // DEBUG
        sendError(rerr);
    } else {
        Packet::free(rerr);
    }

    Packet::free(p);
}

/*
 Packet Transmission Routines
 */

void MAODV::forward(maodv_rt_entry *rt, Packet *p, double delay) {
    struct hdr_cmn *ch = HDR_CMN(p);
    struct hdr_ip *ih = HDR_IP(p);

    if (ih->ttl_ == 0) {

#ifdef DEBUG
        fprintf(stderr, "%s: calling drop()\n", __PRETTY_FUNCTION__);
#endif // DEBUG
        drop(p, DROP_RTR_TTL);
        return;
    }

    if (ch->ptype() != PT_MAODV && ch->direction() == hdr_cmn::UP
            && ((u_int32_t) ih->daddr() == IP_BROADCAST) || (ih->daddr()
            == here_.addr_)) {
        dmux_->recv(p, 0);
        return;
    }

    if (rt) {
        assert(rt->rt_flags == RTF_UP);
        rt->rt_expire = CURRENT_TIME + MADOV_ACTIVE_ROUTE_TIMEOUT;
        ch->next_hop_ = rt->rt_nexthop;
        ch->addr_type() = NS_AF_INET;
        ch->direction() = hdr_cmn::DOWN; //important: change the packet's direction
    } else { // if it is a broadcast packet
        // assert(ch->ptype() == PT_MAODV); // maybe a diff pkt type like gaf
        assert(ih->daddr() == (nsaddr_t) IP_BROADCAST);
        ch->addr_type() = NS_AF_NONE;
        ch->direction() = hdr_cmn::DOWN; //important: change the packet's direction
    }

    if (ih->daddr() == (nsaddr_t) IP_BROADCAST) {
        // If it is a broadcast packet
        assert(rt == 0);
        if (ch->ptype() == PT_MAODV) {
            /*
             *  Jitter the sending of MAODV broadcast packets by 10ms
             */
            Scheduler::instance().schedule(target_, p, 0.01 * Random::uniform());
        } else {
            Scheduler::instance().schedule(target_, p, 0.); // No jitter
        }
    } else { // Not a broadcast packet
        if (delay > 0.0) {
            Scheduler::instance().schedule(target_, p, delay);
        } else {
            // Not a broadcast packet, no delay, send immediately
            Scheduler::instance().schedule(target_, p, 0.);
        }
    }

}

void MAODV::sendRequest(nsaddr_t dst) {
    // Allocate a RREQ packet
    Packet *p = Packet::alloc();
    struct hdr_cmn *ch = HDR_CMN(p);
    struct hdr_ip *ih = HDR_IP(p);
    struct hdr_maodv_request *rq = HDR_MAODV_REQUEST(p);
    maodv_rt_entry *rt = rtable.rt_lookup(dst);

    assert(rt);

    /*
     *  Rate limit sending of Route Requests. We are very conservative
     *  about sending out route requests.
     */

    if (rt->rt_flags == RTF_UP) {
        assert(rt->rt_hops != INFINITY2);
        Packet::free((Packet *) p);
        return;
    }

    if (rt->rt_req_timeout > CURRENT_TIME) {
        Packet::free((Packet *) p);
        return;
    }

    // rt_req_cnt is the no. of times we did network-wide broadcast
    // MADOV_RREQ_RETRIES is the maximum number we will allow before
    // going to a long timeout.

    if (rt->rt_req_cnt > MADOV_RREQ_RETRIES) {
        rt->rt_req_timeout = CURRENT_TIME + MADOV_MAX_RREQ_TIMEOUT;
        rt->rt_req_cnt = 0;
        Packet *buf_pkt;
        while ((buf_pkt = rqueue.deque(rt->rt_dst))) {
            drop(buf_pkt, DROP_RTR_NO_ROUTE);
        }
        Packet::free((Packet *) p);
        return;
    }

#ifdef DEBUG
    fprintf(stderr, "(%2d) - %2d sending Route Request, dst: %d\n",
            ++route_request, index, rt->rt_dst);
#endif // DEBUG
    // Determine the TTL to be used this time.
    // Dynamic TTL evaluation - SRD

    rt->rt_req_last_ttl = max(rt->rt_req_last_ttl,rt->rt_last_hop_count);

    if (0 == rt->rt_req_last_ttl) {
        // first time query broadcast
        ih->ttl_ = MADOV_TTL_START;
    } else {
        // Expanding ring search.
        if (rt->rt_req_last_ttl < MADOV_TTL_THRESHOLD)
            ih->ttl_ = rt->rt_req_last_ttl + MADOV_TTL_INCREMENT;
        else {
            // network-wide broadcast
            ih->ttl_ = MADOV_NETWORK_DIAMETER;
            rt->rt_req_cnt += 1;
        }
    }

    // remember the TTL used  for the next time
    rt->rt_req_last_ttl = ih->ttl_;

    // PerHopTime is the roundtrip time per hop for route requests.
    // The factor 2.0 is just to be safe .. SRD 5/22/99
    // Also note that we are making timeouts to be larger if we have
    // done network wide broadcast before.

    rt->rt_req_timeout = 2.0 * (double) ih->ttl_ * PerHopTime(rt);
    if (rt->rt_req_cnt > 0)
        rt->rt_req_timeout *= rt->rt_req_cnt;
    rt->rt_req_timeout += CURRENT_TIME;

    // Don't let the timeout to be too large, however .. SRD 6/8/99
    if (rt->rt_req_timeout > CURRENT_TIME + MADOV_MAX_RREQ_TIMEOUT)
        rt->rt_req_timeout = CURRENT_TIME + MADOV_MAX_RREQ_TIMEOUT;
    rt->rt_expire = 0;

#ifdef DEBUG
    fprintf(stderr, "(%2d) - %2d sending Route Request, dst: %d, tout %f ms\n",
            ++route_request,
            index, rt->rt_dst,
            rt->rt_req_timeout - CURRENT_TIME);
#endif	// DEBUG

    // Fill out the RREQ packet
    // ch->uid() = 0;
    ch->ptype() = PT_MAODV;
    ch->size() = IP_HDR_LEN + rq->size();
    ch->iface() = -2;
    ch->error() = 0;
    ch->addr_type() = NS_AF_NONE;
    ch->prev_hop_ = index; // MAODV hack

    ih->saddr() = index;
    ih->daddr() = IP_BROADCAST;
    ih->sport() = RT_PORT;
    ih->dport() = RT_PORT;

    // Fill up some more fields.
    rq->rq_type = MAODVTYPE_RREQ;
    rq->rq_hop_count = 1;
    rq->rq_bcast_id = bid++;
    rq->rq_dst = dst;
    rq->rq_dst_seqno = (rt ? rt->rt_seqno : 0);
    rq->rq_src = index;
    seqno += 2;
    assert((seqno % 2) == 0);
    rq->rq_src_seqno = seqno;
    rq->rq_timestamp = CURRENT_TIME;

    Scheduler::instance().schedule(target_, p, 0.);

}

void MAODV::sendReply(nsaddr_t ipdst, u_int32_t hop_count, nsaddr_t rpdst,
        u_int32_t rpseq, u_int32_t lifetime, double timestamp) {
    Packet *p = Packet::alloc();
    struct hdr_cmn *ch = HDR_CMN(p);
    struct hdr_ip *ih = HDR_IP(p);
    struct hdr_maodv_reply *rp = HDR_MAODV_REPLY(p);
    maodv_rt_entry *rt = rtable.rt_lookup(ipdst);

#ifdef DEBUG
    fprintf(stderr, "sending Reply from %d at %.2f\n", index, Scheduler::instance().clock());
#endif // DEBUG
    assert(rt);

    rp->rp_type = MAODVTYPE_RREP;
    //rp->rp_flags = 0x00;
    rp->rp_hop_count = hop_count;
    rp->rp_dst = rpdst;
    rp->rp_dst_seqno = rpseq;
    rp->rp_src = index;
    rp->rp_lifetime = lifetime;
    rp->rp_timestamp = timestamp;

    // ch->uid() = 0;
    ch->ptype() = PT_MAODV;
    ch->size() = IP_HDR_LEN + rp->size();
    ch->iface() = -2;
    ch->error() = 0;
    ch->addr_type() = NS_AF_INET;
    ch->next_hop_ = rt->rt_nexthop;
    ch->prev_hop_ = index; // MAODV hack
    ch->direction() = hdr_cmn::DOWN;

    ih->saddr() = index;
    ih->daddr() = ipdst;
    ih->sport() = RT_PORT;
    ih->dport() = RT_PORT;
    ih->ttl_ = MADOV_NETWORK_DIAMETER;

    Scheduler::instance().schedule(target_, p, 0.);

}

void MAODV::sendError(Packet *p, bool jitter) {
    struct hdr_cmn *ch = HDR_CMN(p);
    struct hdr_ip *ih = HDR_IP(p);
    struct hdr_maodv_error *re = HDR_MAODV_ERROR(p);

#ifdef ERROR
    fprintf(stderr, "sending Error from %d at %.2f\n", index, Scheduler::instance().clock());
#endif // DEBUG
    re->re_type = MAODVTYPE_RERR;
    //re->reserved[0] = 0x00; re->reserved[1] = 0x00;
    // DestCount and list of unreachable destinations are already filled

    // ch->uid() = 0;
    ch->ptype() = PT_MAODV;
    ch->size() = IP_HDR_LEN + re->size();
    ch->iface() = -2;
    ch->error() = 0;
    ch->addr_type() = NS_AF_NONE;
    ch->next_hop_ = 0;
    ch->prev_hop_ = index; // MAODV hack
    ch->direction() = hdr_cmn::DOWN; //important: change the packet's direction

    ih->saddr() = index;
    ih->daddr() = IP_BROADCAST;
    ih->sport() = RT_PORT;
    ih->dport() = RT_PORT;
    ih->ttl_ = 1;

    // Do we need any jitter? Yes
    if (jitter)
        Scheduler::instance().schedule(target_, p, 0.01 * Random::uniform());
    else
        Scheduler::instance().schedule(target_, p, 0.0);

}

/*
 Neighbor Management Functions
 */

void MAODV::sendHello() {
    Packet *p = Packet::alloc();
    struct hdr_cmn *ch = HDR_CMN(p);
    struct hdr_ip *ih = HDR_IP(p);
    struct hdr_maodv_reply *rh = HDR_MAODV_REPLY(p);

#ifdef DEBUG
    fprintf(stderr, "sending Hello from %d at %.2f\n", index, Scheduler::instance().clock());
#endif // DEBUG
    rh->rp_type = MAODVTYPE_HELLO;
    //rh->rp_flags = 0x00;
    rh->rp_hop_count = 1;
    rh->rp_dst = index;
    rh->rp_dst_seqno = seqno;
    rh->rp_lifetime = (1 + MADOV_ALLOWED_HELLO_LOSS) * MADOV_HELLO_INTERVAL;

    // ch->uid() = 0;
    ch->ptype() = PT_MAODV;
    ch->size() = IP_HDR_LEN + rh->size();
    ch->iface() = -2;
    ch->error() = 0;
    ch->addr_type() = NS_AF_NONE;
    ch->prev_hop_ = index; // MAODV hack

    ih->saddr() = index;
    ih->daddr() = IP_BROADCAST;
    ih->sport() = RT_PORT;
    ih->dport() = RT_PORT;
    ih->ttl_ = 1;

    Scheduler::instance().schedule(target_, p, 0.0);
}

void MAODV::recvHello(Packet *p) {
    //struct hdr_ip *ih = HDR_IP(p);
    struct hdr_maodv_reply *rp = HDR_MAODV_REPLY(p);
    MAODV_Neighbor *nb;

    nb = nb_lookup(rp->rp_dst);
    if (nb == 0) {
        nb_insert(rp->rp_dst);
    } else {
        nb->nb_expire = CURRENT_TIME + (1.5 * MADOV_ALLOWED_HELLO_LOSS
                * MADOV_HELLO_INTERVAL);
    }

    Packet::free(p);
}

void MAODV::nb_insert(nsaddr_t id) {
    MAODV_Neighbor *nb = new MAODV_Neighbor(id);

    assert(nb);
    nb->nb_expire = CURRENT_TIME + (1.5 * MADOV_ALLOWED_HELLO_LOSS * MADOV_HELLO_INTERVAL);
    LIST_INSERT_HEAD(&nbhead, nb, nb_link);
    seqno += 2; // set of neighbors changed
    assert((seqno % 2) == 0);
}

MAODV_Neighbor*
MAODV::nb_lookup(nsaddr_t id) {
    MAODV_Neighbor *nb = nbhead.lh_first;

    for (; nb; nb = nb->nb_link.le_next) {
        if (nb->nb_addr == id)
            break;
    }
    return nb;
}

/*
 * Called when we receive *explicit* notification that a Neighbor
 * is no longer reachable.
 */
void MAODV::nb_delete(nsaddr_t id) {
    MAODV_Neighbor *nb = nbhead.lh_first;

    log_link_del(id);
    seqno += 2; // Set of neighbors changed
    assert((seqno % 2) == 0);

    for (; nb; nb = nb->nb_link.le_next) {
        if (nb->nb_addr == id) {
            LIST_REMOVE(nb, nb_link);
            delete nb;
            break;
        }
    }

    handle_link_failure(id);

}

/*
 * Purges all timed-out Neighbor Entries - runs every
 * MADOV_HELLO_INTERVAL * 1.5 seconds.
 */
void MAODV::nb_purge() {
    MAODV_Neighbor *nb = nbhead.lh_first;
    MAODV_Neighbor *nbn;
    double now = CURRENT_TIME;

    for (; nb; nb = nbn) {
        nbn = nb->nb_link.le_next;
        if (nb->nb_expire <= now) {
            nb_delete(nb->nb_addr);
        }
    }
}
